Improved arresting device for hybrid aircraft and arresting method using such a device

Abstract

Hybridized aircraft rotor (200) arresting device (1), particularly for helicopters, the aircraft (200) comprising a turbomachine (100) having at least one gas generator (12), a free turbine (14) driven in rotation by a gas flow generated by the gas generator, and a main rotor (52), the arresting device (1) comprising a first reversible electric machine (30) suitable for being coupled to the main rotor (52), and a second reversible electric machine (40) suitable for being coupled to a high-pressure shaft (18) of the gas generator (12), the first electric machine (30) being configured, when the gas generator (12) is in the stopping phase and the aircraft (200) is on the ground, so as to operate in a generator mode so as to create a torque opposing the rotation of the main rotor (52) to brake the latter,The stopping device (1) includes a control unit (60) configured to control the first electric machine (30) and the second electric machine (40) so as to transfer the electrical energy generated by the first electric machine (30) operating in generator mode to the second electric machine (40) operating in motor mode. Fig. 2.

Description

Title of the invention: Improved arresting device for hybrid aircraft and arresting method using such a device. Technical field

[0001] The present invention relates to the field of hybrid aircraft, comprising at least one turbomachine such as a turboshaft engine or turboprop engine, for flying machines such as helicopters or airplanes. In particular, the invention relates to a stopping device for a hybrid aircraft, a hybrid aircraft comprising such a stopping device, and a stopping method using such a stopping device. Previous technique

[0002] As is known, a turbomachine, for example a turboshaft engine, particularly for a helicopter, comprises a gas turbine having a gas generator and a free turbine driven in rotation by the gas flow generated by the gas generator. In addition, an aircraft, whether hybrid or not, generally includes, besides this turbomachine, a reversible electric machine coupled to the gas generator, so as to rotate the gas generator during a turbomachine start-up phase, or in flight so as to supply the aircraft's non-propulsive electrical requirements.

[0003] Traditionally, the gas generator comprises at least one compressor and one turbine coupled in rotation. The operating principle is as follows: fresh air entering the gas turbine is compressed by the rotation of the compressor before being sent to a combustion chamber where it is mixed with a fuel. The exhaust gases from combustion are then expelled at high speed. A first expansion then occurs in the gas generator turbine, during which the turbine extracts the energy necessary to drive the compressor. The gas generator turbine does not absorb all the kinetic energy of the exhaust gases, and the excess kinetic energy corresponds to the gas flow generated by the gas generator.The latter therefore provides kinetic energy to the free turbine so that a second expansion occurs in the free turbine which transforms this kinetic energy into mechanical energy in order to drive a receiving organ, such as the helicopter rotor.

[0004] During the turbomachine start-up phase, it is necessary to rotate the gas generator, that is, to rotate the compressor coupled to the turbine. As mentioned above, this is precisely one of the roles of the reversible electric machine, known elsewhere, which is most often an electric motor capable of operating reversibly in motor mode or in electric generator mode.

[0005] The rotational drive of the compressor by the reversible electric machine operating in motor mode effectively circulates air within the compressor, thus supplying compressed air to the combustion chamber to initiate combustion. This combustion then produces the gas flow that drives the turbine to rotate, after which the compressor is directly driven in rotation by the turbine, meaning that the gas generator operates autonomously, marking the end of the turbomachine's start-up phase.

[0006] It is known that aircraft, in which such turbomachines are intended to be integrated, include electrical equipment that requires a power supply. For example, a helicopter requires a power supply for its electrical equipment, such as the electric controls, heating, air conditioning, and winch.

[0007] Until now, in flight, the reversible electric machine was used to supply electricity to electrical equipment. To do this, the electric machine, now operating as an electric generator, was driven in rotation by the gas generator, the rotational kinetic energy extracted from the gas generator being converted into electrical energy by said machine. For a helicopter, however, extracting energy from the gas generator has drawbacks. The variation, during flight, of the mechanical power extracted by the electric machine from the gas generator results in a shift in the engine's operating line within the compressor field.This displacement corresponds to a margin in the pumping that must be provisioned, which has the consequence of penalizing the optimization of the engine's operating line, by preventing the use of the compressor at an optimal pressure rate, and consequently degrading stabilized performance, with an impact on specific consumption.

[0008] Document FR2929324 addressed this issue by allowing the same electric machine to start the engine by driving the gas generator, and then to operate in electrical generation mode by drawing power from the free turbine. This solution notably avoids drawing power from the gas generator, thus improving the specific fuel consumption of the gas turbine. However, this architecture does not allow for the injection of mechanical power to the helicopter's main rotor for autorotation assistance, for example.

[0009] Improvements in power density and reliability of electrical chain equipment (storage, conversion, electric machines) now make it possible to consider hybridizing the main rotor, that is, having at least one electric machine connected to the main rotor and capable of supplying it with power. This power, complementary to the turbine power, notably provides a power boost for transient phases (refueling, takeoff, etc.), a boost This provides power to relieve the gas turbine and optimize its lifespan, and also allows for 100% electric operation in the event of a gas turbine failure, for a limited time. Furthermore, this electric machine can be used to generate electricity (for everyday use and / or to recharge batteries).

[0010] To perform these functions, the electrical machine(s) must be sized to a power output much higher than that of the generators / starters usually used, typically one or more hundred kilowatts, instead of around ten kilowatts. It is therefore desirable to combine the two types of electrical machines (the turbine generator / starter and the electric machine connected to the rotor).

[0011] It is known to use such electric machines, and in particular several hybrid architectures, to perform various functions such as starting the gas generator, generating electricity on the ground, or supplying electrical power to the main rotor. Document FR2104791 discloses a device comprising two electric machines for performing such functions.

[0012] Furthermore, existing architectures may involve the use of mechanical parts such as mechanical brakes for braking the main rotor during shutdown phases, or biocable freewheels. However, these mechanical parts are likely to be used frequently and are associated with high criticality. In other words, given the frequent use of the functions to which these mechanical parts are linked, the risks of malfunction are significant, limiting the reliability of the device.

[0013] Furthermore, these mechanical brakes do not always allow the main rotor, particularly the blades in the case of a helicopter, to be locked in a position advantageous to aircraft operators, facilitating, for example, the attachment of the blades to the aircraft structure and maintenance operations. In addition, these mechanical brakes may not sufficiently reduce the autorotation time of the main rotor after engine shutdown. In this respect, the internal engine temperatures may still be high after shutdown, requiring increased cooling, particularly to limit coking, which existing designs do not allow, or do not adequately allow.

[0014] There is therefore a need for a stopping device with an architecture that at least partially addresses the aforementioned drawbacks. Description of the invention

[0015] The present description relates to a rotor arresting device for a hybrid aircraft, in particular a helicopter, the aircraft comprising a turbomachine including at least one gas generator, a free turbine driven in rotation by a gas flow generated by the gas generator, and a main rotor, the arresting device comprising a first reversible electric machine suitable for coupling to the main rotor, and a second reversible electric machine suitable for coupling to a high-pressure shaft of the gas generator, the first electric machine being configured, when the gas generator is in the shutdown phase and the aircraft is on the ground, to operate in a generator mode so as to create a torque opposing the rotation of the main rotor to brake the latter, the stopping device comprising a control unit configured to command the first electric machine and the second electric machine so as to transfer the electrical energy generated by the first electric machine operating in generator mode, to the second electric machine operating in motor mode.

[0016] The first electric machine can ensure the extraction from the free turbine or the main rotor, so as not to affect the performance of the gas generator, or the injection of power onto the main rotor so as to assist it in certain phases of operation.

[0017] Furthermore, according to the present description, these two electric machines can be advantageously used during the shutdown phases of the turbomachine. For the purposes of this description, the shutdown phases are those phases during which the aircraft is on the ground and the gas generator is in a shutdown phase. "In a shutdown phase" means that the internal combustion engine is stopped, the combustion chamber is extinguished, and the rotating parts of the engine rotor may themselves be stopped, or in a deceleration phase before coming to a complete stop. Similarly, during these shutdown phases, the aircraft's main rotor, which includes blades when the aircraft is a helicopter, may still be moving due to its own inertia, even though the gas generator is shut down.

[0018] It will thus be understood that these shutdown phases include situations in which the aircraft has just landed and the turboshaft engine has just been shut down (in other words, has just received a command triggering engine shutdown, implying the cessation of fuel flow and the beginning of the speed drop of the generator shaft and the free turbine), the main rotor still being rotating due to its inertia, but also subsequent situations in which the main rotor blades are set in motion again after having been immobilized, either naturally, for example by the wind, or mechanically by means of an electric machine. Thus, it will be understood that in these shutdown phases, although the gas generator, and therefore the internal combustion engine, is stopped, the aircraft's electrical system remains active in order to control the various electrical equipment, in particular the battery and the electric machines.

[0019] Furthermore, "reversible" means that the first and second electrical machines are each configured to operate in generator mode, in which They are driven in rotation to generate electrical energy, or in motor mode in which they are capable of providing mechanical power.

[0020] Thus, according to the invention, despite the absence of a mechanical brake that would stop the rotation of the main rotor after the gas generator has stopped, it is possible to reduce the downtime of said main rotor, thanks to the first electric machine operating in generator mode. Indeed, since the first electric machine is coupled to the main rotor, the latter drives the rotation of the first electric machine, which thereby creates a resisting torque opposing the rotation of the main rotor. This torque makes it possible to brake the main rotor until it comes to a stop.

[0021] However, the electrical energy thus generated by the first electric machine must be dissipated. To this end, the control unit commands the first electric machine to transfer the electrical energy it generates to the second electric machine. Furthermore, the control unit commands the second electric machine to operate in motor mode.

[0022] Since the second electric machine is coupled to the high-pressure shaft of the gas generator, the operation of the second electric machine in motor mode drives the rotation of the high-pressure body of the gas generator. With the combustion chamber off, the rotation of the high-pressure body ventilates the gas generator, thus enabling faster engine cooling at the end of flight.

[0023] Thus, at least part of the braking energy of the main rotor can be dissipated in the aerodynamic work provided by the high-pressure unit, and in particular the turbomachine compressor. Consequently, the stopping device according to the invention eliminates the need for a mechanical brake, and therefore reduces the risk of failures inherent in the use of mechanical parts, by advantageously and efficiently utilizing the electrical machines already present in the device. Furthermore, this device also eliminates the need for a system to store or dissipate the electrical energy generated by the first electric machine, thanks to the use of this energy to drive the second electric machine in motor mode.

[0024] In particular, the energy dissipated by the first electric machine is put to good use for motor ventilation, thereby improving its cooling. This solution is also advantageous in configurations where the battery is already fully charged and therefore cannot absorb the electrical energy generated by the first electric machine, without the need to add a heat dissipation system as mentioned above.

[0025] In certain embodiments, the first reversible electric machine is able to be coupled to a shaft of the free turbine by means of a first means of switchable coupling, and the second reversible electric machine is suitable for being coupled to the main rotor by means of a second switchable coupling means configured to be activated when the second electric machine rotates in a first direction of rotation, and to be deactivated when the second electric machine rotates in a second direction of rotation opposite to the first direction of rotation, the second reversible electric machine being further suitable for being coupled to the high-pressure shaft of the gas generator by means of a breakable section or a third coupling means.

[0026] It is understood that the second electric machine can be used in one direction of rotation to be mechanically coupled to the gas generator, and in the other direction of rotation to be mechanically coupled to the main rotor.

[0027] By "switchable coupling means", it is understood that the coupling means can be in an activated position in which the components connected to said coupling means are coupled, or in a deactivated position in which said components are decoupled, it being understood that "component" means the electrical machines, the main rotor and the free turbine.

[0028] In some embodiments, the first and second electric machines are electromagnetic machines each comprising a winding, the control unit being configured so that, when the first electric machine is operating in generator mode and the second electric machine is operating in motor mode, it uses a portion of the electrical energy generated by the first electric machine to increase a current through the winding of the first electric machine and / or the second electric machine.

[0029] In some embodiments, the main rotor includes at least one position sensor capable of measuring a position of the main rotor and communicating this position to the control unit, the control unit being capable of controlling the first electric machine in such a way as to increase the generation of electrical energy by said first electric machine so that the main rotor comes to a stop in a predetermined position measured by the position sensor.

[0030] In certain embodiments, when the aircraft is a helicopter comprising a tail boom, the main rotor comprising blades, the predetermined position is a position in which one of the blades of the main rotor is positioned vertically above the tail boom of the helicopter.

[0031] The present description also relates to a hybrid aircraft comprising a turbomachine having at least one gas generator, a free turbine driven in rotation by a gas flow generated by the gas generator, a main rotor, and comprising a stopping device according to any of the preceding embodiments.

[0032] In some embodiments, the hybrid aircraft is a helicopter.

[0033] The present description also relates to a rotor shutdown method using a hybrid aircraft arresting device according to any of the preceding embodiments, wherein, when the gas generator is shut down and the aircraft is on the ground, the method comprises: - the control of the first reversible electric machine, by the control unit, so as to operate in generator mode in order to create a torque opposing the rotation of the main rotor to brake the latter, - the control of the second reversible electric machine, by the control unit, so as to operate in motor mode in order to drive the high-pressure shaft of the gas generator, - the transfer of electrical energy generated by the first electrical machine operating in generator mode, to the second electrical machine operating in motor mode.

[0034] In some embodiments, the stopping device includes a battery.

[0035] In some embodiments, the process includes a detection step of a battery charge level, such that the step of transferring the electrical energy generated by the first electric machine includes the transfer of a part of said electrical energy generated by the first electric machine to the battery, when a battery charge level is less than or equal to a predetermined threshold value.

[0036] In some embodiments, the method includes detecting a rotational speed of the main rotor and, when the rotational speed of the main rotor is less than or equal to a predetermined value, transferring electrical energy from the battery to the first electric machine operating in generator mode.

[0037] In some embodiments, the stopping device includes a position sensor capable of measuring a position of the main rotor and communicating this position to the control unit, the method including the regulation, by the control unit, of the electrical energy generated by the first electric machine as a function of the position of the main rotor, so as to immobilize the main rotor in a predetermined position.

[0038] In certain embodiments, the method includes, after immobilizing the main rotor in the predetermined position, controlling the first electric machine in motor mode so as to rotate the main rotor, and / or controlling the second electric machine in motor mode so as to rotate the high-pressure shaft of the gas generator, during a maintenance operation.

[0039] In some embodiments, the control unit commands the battery so that the battery supplies electrical power to the first electric machine and / or the second electric machine during the maintenance operation.

[0040] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description of examples of embodiments of the stopping device. This detailed description refers to the accompanying drawings. Brief description of the drawings

[0041] The accompanying drawings are schematic and are intended primarily to illustrate the principles of the exposition. On these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference symbols.

[0042] [Fig-1] Figure [Fig.1] shows a cross-sectional view of a turbomachine according to the invention,

[0043] [Fig.2] Fig.2 schematically represents one embodiment of a device to stop the invention,

[0044] [Fig.3] Fig.3 represents the stopping device of Fig.2, according to a first mode of operation during a shutdown procedure,

[0045] [Fig.4] Fig.4 represents the stopping device of Fig.2, according to a second operating mode during a shutdown procedure,

[0046] [Fig. 5] Fig. 5 represents the stopping device of Fig. 2, according to a third operating mode during a shutdown procedure,

[0047] [Fig.6] Fig.6 represents the stopping device of Fig.2, according to a fourth operating mode during a shutdown procedure,

[0048] [Fig.7] Fig.7 represents in perspective an aircraft according to the invention. Description of the implementation methods

[0049] To make the explanation more concrete, an example of a device and method for stopping the device is described in detail below, with reference to the accompanying drawings. It should be noted that the invention is not limited to this example.

[0050] Fig. 1 schematically represents a turbomachine 100 conforming to the present description, intended in particular to drive in rotation transmission components 50 of a helicopter carrying a propeller or a main rotor 52.

[0051] It should also be noted in general that, for the sake of clarity, Figures 2 to 6 schematically and functionally represent a stopping device 1 and its operating mode, without showing all the details of the components of the turbomachine and the various power transmission elements. In particular, the gears and any speed ratios are not shown.

[0052] The turbomachine 100 comprises a gas turbine 10 having a gas generator 12 and a free turbine 14 capable of being driven into rotation by a gas flow generated by The gas generator 12. The free turbine 14 is mounted on a shaft 16 which transmits the rotational motion to a receiving element such as a main rotor 52 of the helicopter via the transmission elements 50. According to this example, the gas turbine 10 shown in [Fig. 1] is of the front-drive type with coaxial shaft drive. Without departing from the scope of the present invention, one could also consider a free turbine gas turbine of the front-drive type with internal or external shaft drive, or a free turbine turbomachine of the rear-drive or vertical-drive type.

[0053] The gas generator 12 comprises a rotating shaft 18 on which a compressor 20 and a turbine 22 are mounted, as well as a combustion chamber 24 arranged axially between the compressor 20 and the turbine when the gas generator 12 is considered along the axial direction of the rotating shaft 18. The gas turbine 10 has a casing 26 equipped with an air inlet 28 through which fresh air enters the gas generator 12. After its admission into the enclosure of the gas generator 12, the fresh air is compressed by the compressor 20 which forces it towards the inlet of the combustion chamber 24 where it is mixed with fuel. The combustion which takes place in the combustion chamber 24 causes the burnt gases to be evacuated at high speed towards the turbine 22, which in turn causes the shaft 18 of the gas generator 12 to rotate and, consequently, the compressor 20.The rotational speed of the shaft 18 of the gas generator 12 is determined by the fuel flow rate entering the combustion chamber 24.

[0054] Despite the extraction of kinetic energy by the turbine 22, the gas flow exiting the gas generator possesses significant kinetic energy. As can be seen from [Fig. 1], the gas flow F is directed towards the free turbine 14, which causes an expansion in the free turbine 14, leading to the rotation of the turbine wheel and shaft 16.

[0055] A stopping device 1 comprises a first reversible electric machine 30, in this case consisting of an electric motor capable of operating reversibly as an electric generator. It should be noted that although the first reversible electric machine 30 can be located within the turbomachine perimeter, this arrangement is not limiting. The reversible electric machine 30 can indeed be located within perimeters of the helicopter separate from the turbomachine 100, without departing from the scope of the invention. This observation applies generally to the entire stopping device, which also includes the second electric machine and the various coupling means described below. The first reversible electric machine 30 is mechanically coupled to the shaft 16 of the free turbine 14 by means of a first switchable coupling means 32.

[0056] Preferably, the first switchable coupling means 32 comprises a freewheel mounted such that the rotation of the shaft 16 can drive the main rotor 52 and the first electric machine 30 when the latter is operating in generator mode to supply electricity, but conversely, the rotation of the first electric machine 30 cannot drive the shaft 16 of the freewheel 14. In other words, the freewheel of the first coupling means 32 can only transfer rotational torque in the direction from the freewheel 14 to the first main rotor 52 and the first electric machine 30, but not the other way around. On a helicopter, this freewheel is commonly called a "motor freewheel".

[0057] One advantage of a freewheel is that it does not require electronic or mechanical control by an external operator. Such a freewheel generally consists of a hub and a peripheral ring mounted for rotation on the hub. The hub can usually rotate the peripheral ring, but not the other way around. Therefore, the hub can only drive the ring when it rotates in a predetermined direction relative to the ring, which will be called the "direction of engagement." Otherwise, the hub and the peripheral ring rotate freely relative to each other. In this case, the switchable coupling means are activated when the freewheel hub rotates the peripheral ring, and conversely, the switchable coupling means are deactivated when the freewheel hub does not rotate the peripheral ring.

[0058] It should be noted that the use of a freewheel for the disabling coupling means is not limiting, the freewheel being able to be replaced by any dog ​​clutch or clutch system.

[0059] The first electric machine 30 is also suitable for being coupled to the main rotor 52 in such a way that the first electric machine 30, operating in electric motor mode, is suitable for driving the main rotor 52 in rotation. As indicated above, the first electric machine 30 in electric motor mode can drive the main rotor 52 in rotation, but not the free turbine 14, given the presence of the free wheel of the first coupling means 32.

[0060] The stopping device according to the present description further comprises a second reversible electric machine 40, preferably similar to the first reversible electric machine 30, but not necessarily so. In particular, the second reversible electric machine 40 is capable of operating reversibly as an electric generator.

[0061] It should be noted that the power of the second electric machine 40 is on the order of one or several hundred kilowatts. It is possible to start the turbine much more quickly than with a starter with a power of on the order of 10 kW. commonly used. This provides an operational advantage, particularly in the case of medical rescue missions or during attempts at rapid in-flight restarts.

[0062] As described below, it is possible to reverse the direction of rotation of the second reversible electric machine 40, so that the latter is able to operate in all four quadrants of operation, i.e. in generator mode or in motor mode in one direction of rotation, and in generator mode or in motor mode in the other direction of rotation.

[0063] The second reversible electric machine 40 is mechanically coupled to the shaft 18 of the gas generator 12, which is a shaft of the high-pressure casing of the gas turbine 10, via a breakable section 69. The breakable section 69 can be a portion of the shaft connecting the gas generator 12 to the second reversible electric machine 40, which is mechanically weaker (for example, thinner or of a smaller cross-section) than the rest of the shaft, such that a lower torque than for the rest of the shaft is required to break this portion of the shaft. In other words, by increasing the torque applied to the shaft, the first portion of the shaft to mechanically fail will be the breakable section 69.

[0064] It should be noted that the use of a breakable section 69 to couple the second reversible electric machine 40 and the gas generator 12 is not limiting. It is also possible to couple the second reversible electric machine 40 and the gas generator 12 by means of a switchable coupling means similar to the first coupling means 32, including in particular a freewheel.

[0065] The second electric machine 40 is also suitable for being coupled to the main rotor 52, via a second switchable coupling means 42 similar to the first coupling means 32 and preferably comprising a freewheel, in such a way that the second electric machine 40, operating in electric motor mode (second coupling means 42 activated), is suitable for driving the main rotor 52 in rotation.

[0066] According to the architecture of the present exposition, the second electric machine 40 is capable of rotating in a first direction of rotation in which it is mechanically coupled to the main rotor 52, and in a second direction of rotation, opposite to the first direction of rotation, in which it is mechanically coupled to the shaft 18 of the gas generator 12 via the breakable section 69.

[0067] By convention, in the following description, a positive direction, or clockwise direction SH, will be understood as a direction of rotation of the second electrical machine 40 in which the second coupling means 42 is deactivated, and a negative direction, or counterclockwise direction SIH, will be understood as a direction of rotation of the second electrical machine 40 in which the second coupling means 42 is activated. In particular, the element represented by "-1" in [Fig. 2] and the following figures, this represents gears, for example pinions, allowing the direction of rotation to be reversed. It will thus be understood that when the second electrical machine 40 rotates in the positive direction, the second coupling means 42 is deactivated, and when the second electrical machine 40 rotates in the negative direction, the second coupling means 42 can be activated.

[0068] Furthermore, the first electric machine 30 can also be coupled to the main rotor 52 and the turbine shaft 16 via a breakable section 68, similar to the breakable section 69. This breakable section 68 can be useful for decoupling the main rotor 52 from the first electric machine 30, in the event of a blockage of the rotor of the first electric machine 30, in order to limit the power draw from the main rotor 52 and to avoid damage to the transmission components 50.

[0069] Furthermore, the first electric machine 30 is electrically connected to the second electric machine 40 via electrical connections 70, each of the electric machines being further connected to a battery 72. The electrical connections 70 may include electrical conditioning devices (rectifiers, inverters, voltage converters). These connections 70 allow the electric machines 30, 40 to draw power from the battery 72 when operating in motor mode, or conversely, to recharge the battery 72 when operating in generator mode. These connections 70 also allow the electric machines 30, 40 to exchange electrical power with each other.

[0070] For example, this allows the first electric machine 30, connected to the main rotor 52 and the free turbine 14, to take electrical power and transmit it in the form of electric current via the electrical connection 70 to the second electric machine 40, which then returns it to the gas generator 12. It is thus possible to transfer electrical power from the main rotor 52 to the gas generator 12, in certain flight phases requiring such a transfer, or in stopping phases.

[0071] It should be noted that the shutdown phases are the phases during which the aircraft is on the ground, and the gas generator 12 is shut down or in the process of shutting down. In other words, the internal combustion engine is stopped and the combustion chamber 24 is extinguished. More precisely, during these shutdown phases, the aircraft's main rotor 52, which includes blades when the aircraft is a helicopter, may still be in motion, even though the gas generator 12 is extinguished.

[0072] The stopping device 1 also includes a control unit 60 of the "FADEC" type (for "Full Authority Digital Engine Control"), which controls, in particular, the electrical machines 30, 40. It should be noted that the control unit 60 can also monitor the battery 72 to determine its state of charge. It should be noted that the The various connections between control unit 60 and the elements it controls are not shown.

[0073] A stopping method according to one embodiment, using the stopping device 1 described above, is shown in [Fig. 3]. In this figure and the following ones, the dashed arrows represent the direction of mechanical or electrical power transmission between two elements. In [Fig. 3], for example, mechanical power is transmitted from the main rotor 52 to the first electric machine 30, the latter operating in generator mode, and transferring electrical power to the second electric machine 40.

[0074] Such a method makes it possible to brake the rotation of the main rotor 52, after the gas generator 12 has stopped when the aircraft is on the ground, and thus to stop the main rotor.

[0075] Thus, during this shutdown phase, the control unit 60 commands the first electric machine 30 to operate in generator mode. Since the first electric machine 30 is coupled to the main rotor 52, the latter drives the rotation of the first electric machine 30, which thereby creates a resistive torque opposing the rotation of the main rotor 52. This torque allows the main rotor 52 to be braked until it comes to a complete stop. For example, it is possible to dissipate 500 kilojoules (kJ) in less than twenty seconds.

[0076] Furthermore, the control unit 60 commands the first electric machine 30 to transfer the electrical energy generated by the first electric machine 30 to the second electric machine 40, and commands the second electric machine 40 to operate in motor mode.

[0077] As the second electric machine 40 is coupled to the high-pressure shaft 18 of the gas generator 12, the operation in motor mode of the second electric machine 40, rotating in the SH direction, causes the high-pressure body of the gas generator 12 to rotate. With the combustion chamber 24 off, the rotation of the high-pressure body allows the gas generator 12 to be ventilated, which allows the engine to cool down more quickly at the end of flight.

[0078] This configuration is particularly advantageous when the charge level of the battery 72, which can be detected by the control unit 60, is too high to be able to absorb the electrical energy generated by the first electric machine 30.

[0079] However, in one embodiment shown in [Fig. 4], the method may include a step for detecting the charge level of the battery 72. When the charge level of the battery 72 is less than or equal to a predetermined threshold value, for example 80% of the total charge, the transfer of electrical energy generated by the first electric machine 30 may include, in addition to the transfer to the second electric machine 40, the transfer of part of the electrical energy generated by the first electric machine 30 to the battery 72.

[0080] This also allows the electrical energy generated by the first electric machine 30 to be used to recharge the battery 72, and thus to optimize the operation of the device 1. It should be noted, however, that the device can only transfer the electrical energy generated by the first electric machine 30 to the second electric machine 40, even if the charge level of the battery 72 is less than or equal to the predetermined threshold value.

[0081] Optionally, the control unit 60 can control the first electric machine 30 and / or the second electric machine 40 so as to increase the electric current passing through the winding of these electric machines, which are electromagnetic machines.

[0082] In other words, in addition to the current useful for generating the torque enabling the first electric machine 30 to operate in generator mode, and the second electric machine 40 to operate in motor mode, a surplus of current flows through the windings of the electric machines.

[0083] This excess current, called flux deflux current, increases the heating of the windings and thus amplifies heat dissipation. Indeed, the current flowing in the windings of the electric machines produces ohmic dissipation proportional to the square of the electric current. The electrical energy generated by the first electric machine 30 is thus also dissipated thermally through these windings. It should be noted that the flux deflux current produces heat dissipation without generating additional torque by the second electric machine 40. This makes it possible to increase the braking force of the main rotor 52 while limiting the drive speed of the gas generator 12 by the second electric machine 40.

[0084] This configuration is advantageous when it is necessary to further accelerate the stopping of the rotor, in other words to reduce the time required to slow down the main rotor 52, and to immobilize the latter, or if the ventilation produced by the high-pressure body of the gas generator 12 is not sufficient to dissipate energy allowing the immobilization of the main rotor 52.

[0085] Preferably, the stopping device 1 may include a position sensor 19, allowing the measurement of an angular position of the main rotor 52, the position sensor 19 being able to communicate this position to the control unit 60.

[0086] Figure 7 represents an aircraft, which is a helicopter 200 in this example, comprising such a position sensor 19. The position sensor 19 can be arranged in the vertical mast of the main rotor 52, driving the blades 54 fixed to said vertical mast. The position sensor 19 can also be arranged on gears intermediate transmission components 50 which drive the blades 54, or in the tail boom 220 so as to detect the passage of the blades 54 vertically above the sensor (in this case the sensor 19 can be an optical sensor with a window through the cowlings to make the blades visible).

[0087] By these arrangements, the position sensor 19 makes it possible to measure an absolute position of the main rotor 52, and therefore of the blades 54. Indeed, given the reduction ratio of the transmission between the first electric machine 30 and the main rotor 52, placing the position sensor 19 on the first electric machine 30 would only allow the determination of a relative position of the main rotor 52, a given angular position of the main rotor 52 being able to correspond to several positions of the first electric machine 30.

[0088] The position sensor 19 can be a resolver, or an optical or magnetic encoder wheel, allowing continuous measurement of the angular position of the main rotor shaft 52.

[0089] Alternatively, the position sensor 19 can be a point-passage detector, located for example on a blade 54, cooperating with a second detector located on the aircraft, for example on the tail boom 220 (or tail pylon) of the helicopter 200. This point detector makes it possible to detect each alignment of the blade 54 with the tail boom 220, and therefore the passage of this blade 54 at each complete revolution. This detection, which can be called a "top revolution," can be achieved by optical, mechanical, magnetic, or capacitive means. The control unit 60 can then reconstruct the position of the blade 54, and therefore of the main rotor 52, continuously between two passes, i.e., between two "top revolutions."

[0090] Based on this position information provided by the position sensor 19, the control unit 60 commands the first electric machine 30 so as to increase the generation of electrical energy by said first electric machine 30 so that the main rotor 52 comes to a stop in a predetermined position measured by the position sensor 19.

[0091] Preferably, the predetermined position is a preferred position for the aircraft operator. It should be noted that this preferred position may depend on the number of blades comprising the main rotor 52. However, the preferred position is typically one in which one of the blades 54 of the main rotor 52 is positioned vertically above the tail boom 220 of the helicopter 200, in the position shown in [Fig. 7].

[0092] It is therefore understood that the control unit 60 controls the first electric machine 30 in such a way as to adjust the level of electrical energy generation by the latter, and therefore in such a way as to adjust the braking induced on the main rotor 52, according to the position of the main rotor 52 measured by the position sensor 19. In other words, the control unit 60 modulates the electric current generated by the first electric machine 30 to control the stopping position of the main rotor 52. There is therefore a servo control of the first electric machine 30 on the position setpoint coming from the position sensor 19 of the main rotor 52.

[0093] For example, when the main rotor 52 is rotating at low speed, close to stopping, the control unit 60 can detect, by means of the position sensor 19, that the main rotor 52 is approaching the predetermined stopping position, and command the first electric machine 30 to increase the generation of electrical energy so that the main rotor 52 stops in said predetermined position.

[0094] Controlling the slowing down of the main rotor 52, and its immobilization in this predetermined position, makes it easier to install the blade attachments 230, which serve to limit the movements of the rotor when stopped and which connect each blade 54 to an element of the structure of the helicopter 200, for example, the tail boom 220, the feet 240 and the front nose of the helicopter 200, as illustrated in [Fig.7].

[0095] Furthermore, according to the configuration shown in [Fig.5], the method may include the detection of a rotational speed of the main rotor 52, for example by a position sensor or a speed sensor and, when the rotational speed of the main rotor 52 is less than or equal to a predetermined speed value, the control of the battery 72 by the control unit 60, so as to transfer electrical energy from the battery 72 to the first electric machine 30 operating in generator mode.

[0096] This supply of electrical energy to the first electric machine 30 by the battery 72 makes it possible to maintain control over this first electric machine 30, and to obtain a complete stop of the main rotor 52. Indeed, when the main rotor 52 is close to stopping and is rotating at low speed, the electrical voltage in the first electric machine 30 is too low for the first electric machine 30 to be able to operate in generator mode.

[0097] Without control of the first electric machine 30, the latter could no longer fulfill its braking function effectively, and the rotor could continue to rotate at low speed for a longer time before its complete stop.

[0098] The supply of voltage by the battery 72 when the rotational speed of the main rotor 52 is less than or equal to a predetermined speed value allows the first electric machine 30 to continue to operate in generator mode until the complete stop of the main rotor 52.

[0099] Furthermore, according to the configuration shown in [Fig. 6], the method may include, after the main rotor 52 has been immobilized in the predetermined position, the control, by the control unit 60, of the first machine electric 30 in motor mode so as to rotate the main rotor 52, and / or the control of the second electric machine 40 also in motor mode, so as to rotate the high pressure shaft 18 of the gas generator 12, during a maintenance operation.

[0100] To do this, the control unit 60 can control the battery 72 so that the battery 72 supplies electrical power to the first electric machine 30 and / or the second electric machine 40 during the maintenance operation.

[0101] It will be noted that, in a configuration not shown, the second electric machine 40 can also operate in motor mode by rotating in the SIH direction, so as to rotate the main rotor 52, instead of, or in assistance to, the first electric machine 30. In this case, the section to be broken can be replaced by a free wheel.

[0102] This configuration allows the electric machines 30, 40 to be used efficiently, via the battery 72, to perform occasional maintenance operations on the aircraft when it is on the ground with the engine off. This allows, for example, compressor cleaning (known as "dry ventilation") with the combustion chamber off, vibration analysis of the rotating moving parts, analysis of resisting torque to detect potential failures in the rotating assemblies, and more precise control of the endoscopic inspection of the rotating assemblies.

[0103] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0104] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. A hybrid aircraft (200) rotor arresting device (1), particularly for a helicopter, the aircraft (200) comprising a turbomachine (100) having at least one gas generator (12), a free turbine (14) driven in rotation by a gas flow generated by the gas generator, and a main rotor (52), the arresting device (1) comprising a first reversible electric machine (30) capable of being coupled to the main rotor (52), and a second reversible electric machine (40) capable of being coupled to a high-pressure shaft (18) of the gas generator (12), the first electric machine (30) being configured, when the gas generator (12) is in the stopping phase and the aircraft (200) is on the ground, to operate in a generator mode so as to create a torque opposing the rotation of the main rotor (52) to brake the latter,the stopping device (1) comprising a control unit (60) configured to control the first electric machine (30) and the second electric machine (40) so as to transfer the electrical energy generated by the first electric machine (30) operating in generator mode, to the second electric machine (40) operating in motor mode.

2. A stopping device (1) according to claim 1, wherein the first reversible electric machine (30) is able to be coupled to a shaft (16) of the free turbine (14) by means of a first switchable coupling means (32), and the second reversible electric machine (40) is able to be coupled to the main rotor (52) by means of a second switchable coupling means (42) configured to be activated when the second electric machine (40) rotates in a first direction of rotation (SIH), and to be deactivated when the second electric machine (40) rotates in a second direction of rotation (SH) opposite to the first direction of rotation (SIH), the second reversible electric machine (40) further being able to be coupled to the high-pressure shaft (18) of the gas generator (12) by means of a breakable section (69) or a third coupling means.

3. Stopping device (1) according to claim 1 or 2, wherein the first and second electrical machines (30, 40) are electromagnetic machines, each comprising a winding, the control unit (60) being configured so that, when the first electric machine (30) is operating in generator mode and the second electric machine (40) is operating in motor mode, it uses a portion of the electrical energy generated by the first electric machine (30) to increase a current through the winding of the first electric machine (30) and / or the second electric machine (40).

4. Stopping device (1) according to any one of claims 1 to 3, wherein the main rotor (52) comprises at least one position sensor (19) capable of measuring a position of the main rotor (52) and communicating this position to the control unit (60), the control unit (60) being capable of controlling the first electric machine (30) so as to increase the generation of electrical energy by said first electric machine (30) so that the main rotor (52) comes to a stop in a predetermined position measured by the position sensor (19).

5. Stopping device (1) according to claim 4, wherein, when the aircraft (200) is a helicopter comprising a tail boom (220), the main rotor (52) comprising blades (54), the predetermined position is a position in which one of the blades (54) of the main rotor (52) is positioned vertically above the tail boom (220) of the helicopter.

6. Hybridized aircraft (200) comprising a turbomachine (100) having at least one gas generator (12), a free turbine (14) driven in rotation by a gas flow generated by the gas generator (12), a main rotor (52), and comprising a stopping device (1) according to any one of claims 1 to 5.

7. Hybridized aircraft (200) according to claim 6, the hybridized aircraft being a helicopter.

8. A rotor stopping method using a stopping device (1) for a hybrid aircraft (200) according to any one of claims 1 to 5, wherein, when the gas generator (12) is stopped and the aircraft is on the ground, the method comprises: - the control of the first reversible electric machine (30), by the control unit (60), so as to operate in generator mode in order to create a torque opposing the rotation of the main rotor (52) to brake the latter, - the control of the second reversible electric machine (40), by the control unit (60), so as to operate in motor mode in order to drive the high pressure shaft (18) of the gas generator (12), - the transfer of the electrical energy generated by the first electric machine (30) operating in generator mode, to the second electric machine (40) operating in motor mode.

9. A method according to claim 8, wherein the stopping device (1) comprises a battery (72), the method comprising a step of detecting a charge level of the battery (72), such that the step of transferring the electrical energy generated by the first electric machine (30) comprises the transfer of a part of said electrical energy generated by the first electric machine (30) to the battery (72), when a charge level of the battery (72) is less than or equal to a predetermined threshold value.

10. A method according to claim 9, comprising detecting a rotational speed of the main rotor (52) and, when the rotational speed of the main rotor (52) is less than or equal to a predetermined value, transferring electrical energy from the battery (72) to the first electric machine (30) operating in generator mode.

11. A method according to any one of claims 8 to 10, wherein the stopping device (1) comprises a position sensor (19) capable of measuring a position of the main rotor (52) and communicating this position to the control unit (60), the method comprising the regulation, by the control unit (60), of the electrical energy generated by the first electric machine (30) as a function of the position of the main rotor (52), so as to immobilize the main rotor (52) in a predetermined position.

12. A method according to claim 11, comprising, after immobilizing the main rotor (52) in the predetermined position, controlling the first electric machine (30) in motor mode so as to rotate the main rotor (52), and / or controlling the second electric machine (40) in motor mode so as to rotate the high-pressure shaft (18) of the gas generator (12), during a maintenance operation. 21

13. A method according to claim 12, wherein the control unit (60) controls the battery (72) so that the battery (72) supplies electrical power to the first electric machine (30) and / or the second electric machine (40) during the maintenance operation.

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